Diaries, when they do manage to survive, achieve a status that would never have been expected by their authors. These often intensely private records offer a compellingly intimate window into lives and times past. But consciously providing such records for others is seldom the driving motive. Most diarists reckon their output to be private, after all.

I've never got past January 8 with my own efforts, but I love other people's diaries. They are among the most interesting, precious and usually unappreciated types of human record. So, I collect them, or rather, rescue them, because private diaries of un-famous people in this country are usually, ultimately doomed. They are supposed to be private, true, and they are often grubby or hard to read; they are thus unloved, uncared for, burned, skipped, torn up or left to moulder into green lumps in cellars. My dream is to start a campaign to rescue them, not the diaries of the famous, but the everyday diaries of private individuals, whose private hopes and fears should also be preserved.

So, rescue. Not so that we can pry and poke in our noses right now, but so that the wee volumes can be preserved for readers in 100 or 200 years' time. We need to save them in some fire-proofed vault for unborn readers, for whom the 20th and 21st centuries will seem distant and unreal. But human words and thoughts will bring them, and their worlds, back to life.

Few enough diarists see their work from any kind of external viewpoint. Most diarists that I have met just do it: having started, they can no more go to bed without filling out the day's entry than without cleaning their teeth. A diary is a companion; it is reliable, silent, unprotesting, accommodating and, as it builds up, provides a wonderful set of trigger mechanisms to recall detail of past life and experience. This is a very private process, but these private documents have a wider importance, not appreciated by the normal diarist.

I should have liked to take tea with the abnormal Rev Robert Shields, even if he would have broken off conversation every few minutes to record crumbs of cake in my beard. For among all diarists who ever wielded a pencil (or in his case, a bank of electric typewriters), this man was unique. For 25 years, he spent four hours a day transcribing what he had done and thought - from the profound to the astonishingly mundane (lightbulb-changing features at regular intervals) - in five-minute sections.

A stroke brought the journal to an end, all 37m words of it, in 1997. With his death last month in Dayton, Washington, aged 89, the diaries have at his request now passed into the hands of the Washingston State University library. They are, in their distinctly eccentric fashion, an unparalleled record of one life in its most minute detail.

No one, I think, has ever quite achieved such a feat before. There are long diaries and very long diaries (my longest find is actually 76 volumes), and all manner of shapes and sizes in between, but it is surely true that no one has conceived such a project as this and carried it through so unwaveringly. The librarians at Washington State might groan at archiving its 91 volumes, but in time Robert Shields will join Samuel Pepys in some cosmic gallery of diarists, if they are not already having tea somewhere together. If so, I guess the Reverend is casting around for his typewriter.